Time too good to be true

Kleppner calls attention to a couple of issues concerning time. The issue regarding whether to retain or phase out leap seconds is merely calendraic. However, a second issue concerns the future of time itself. At accuracies beyond one part in ten to the 16th power, the gravitational blueshift, predicted by general relativity, scrambles time with Earth's gravity in a rather unmanageable fashion that ultimately upsets what is meant by keeping time.